1. Field of the Invention
The present invention relates to an electrical scanning probe microscope, particularly to a front-wing cantilever for the conductive probe of the electrical scanning probe microscope, which can avoid the optical perturbation.
2. Description of the Related Art
Electrical Scanning Probe Microscopy (ESPM), which is a widely applied technology for surface electrical property analysis, has the characteristics of easy performance and can directly and rapidly provide the nanometric electrical information of material surface, such as the variations of current, resistance, and capacitance, and the information gained thereby has the advantage of high accuracy. Via the conductive probe contacting the surface of a specimen, various applications of Electrical Scanning Probe Microscopy can be evolved, such as Scanning Capacitance Microscopy (SCM), Scanning Spreading Resistance Microscopy (SSRM), and Conductive Atomic Force Microscopy (CAFM).
Herein, Electrical Scanning Probe Microscopy (ESPM) is to be exemplified by the Scanning Capacitance Microscope, which utilizes a phase-lock amplifier to amplify the detected small signal, and wherein a modulation voltage, which is an AC bias with a specific frequency and amplitude, is applied to the specimen surface via a conductive probe, and the frequency of the modulation voltage is feedback to the system's phase-lock amplifier to be a reference frequency. The signal of capacitance variation in the specimen surface, which is induced by the modulation voltage, also has the same specific frequency, and when the signal of capacitance variation is input to the phase-lock amplifier, the phase-lock amplifier can amplify the weak signal with the same specific frequency via the reference frequency. Therefore, the Scanning Capacitance Microscope has a very high sensitivity.
The conventional Scanning Capacitance Microscope generally adopts a conductive probe with a flattened type or a V type cantilever and a red laser as the optical-beam-deflection image-forming architecture of the atomic force microscope in order to synchronically obtain the topographic image and the corresponding differential capacitance image. As shown in FIG. 1, the conventional cantilever structure 10 has: a cantilever holder 12; a cantilever 14, extending out from the cantilever holder 12; and a tip 16, installed below the end of the cantilever 14. The conventional cantilever structure has the following disadvantages:                1. The contrast of a differential capacitance image is inferior. The stray light from the red laser results in optical absorption, which further induces carrier injection. The carrier injection results in less difference between the differential capacitance signals of low and high carrier concentration regions. Thus, the contrast of differential capacitance image becomes small.        2. The measured electrical junction width is smaller than the real one. The photovoltaic effect created by the optical absorption results in that the measured junction width is smaller than the real one. Thus, P-N junction width measured thereby is inaccurate.        3. As the optical perturbation results from the optical absorption of material, the above problems will become more serious for narrow energy gap materials, such as Si1-xGex, GaAs, InP, etc.        
To solve the aforementioned problems, the present invention proposes a front-wing cantilever for a conductive probe of an electrical scanning probe microscope, which not only can avoid the optical perturbation on the measurement and analysis of electrical signals but also can still analyze the topography of material's surface synchronically.